Fluid ejectors have been developed for ink-jet printing. Many different and varied designs of fluid ejectors have been developed in the prior art. Of particular interest are fluid ejectors that can be fabricated using micromachining which allows batch fabrication without piece-part assembly thereby potentially reducing manufacturing costs. Examples of fluid ejectors formed by micromachining can be found in U.S. Pat. Nos. 6,350,015; 6,357,865; 6,364,460; 6,367,915; 6,406,130; 6,409,311; 6,416,169; 6,419,335; 6,472,332; and 6,505,912, each of which is incorporated herein by reference.
A disadvantage of many of the types of fluid ejectors disclosed in the above patents is that these fluid ejectors rely on a high internal electric field for ejection of the fluid (i.e. the fluid is exposed to a high electric field); and this limits the types of fluids that can be used to those types of fluids which are not electrically conductive and which are not chemically alterable in the presence of an electric field.
The present invention provides a surface-micromachined fluid-ejection apparatus (i.e. a fluid ejector) wherein the fluid is not exposed to any electric field prior to ejection thereof, and thereby allowing the use of many different types of fluids including electrically-conductive fluids, multi-component fluids, fluids containing electrically-conductive solid particles, and fluids which undergo an unwanted chemical reaction in the presence of an electric field, etc.
The present invention also provides a fluid ejector in which a force and/or displacement used to eject a jet or drop of a particular fluid can be controlled and varied, thereby allowing the fluid ejector of the present invention to be used with a wide range of fluids of different viscosity, and further allowing the amount of fluid ejected to be controlled and varied to produce droplet sizes in the range of less than one femtoliter to picoliters or larger.
In certain embodiments of the present invention, two or more different fluids can be mixed or combined immediately prior to ejection thereof to provide an ejecta having characteristics not heretofore possible with conventional fluid ejection devices.
Embodiments of the present invention can be provided with different types of microelectromechanical (MEM) actuators including electrostatic comb actuators, capacitively-coupled electrostatic plate actuators and thermal actuators.
These and other advantages of the present invention will become evident to those skilled in the art.